Residential and commercial pool filtration systems are known in the art. Typically these systems comprise a skimmer intake with a basket-like trap for retaining large debris such as leaves that flout on the surface of a pool, and a drain intake for pulling water from the bottom of the pool where sediment and other non-floating debris collects. Occasionally, the lines for the skimmer and drain intake merge into a single line which passes through a main pool filter, usually comprising a fine mesh, caked with a filtering media such as diatomaceous earth or cellulose fiber.
Small particulate debris taken in by the drain, and to a lesser extent having passed through the skimmer and trap, is collected by the filter and filtering media, which must be cleaned periodically. Cleaning the pool filter is a labor intensive, messy and water wasting task as it involves rinsing debris from the filter, possibly backwashing the filter, replacing the filter media and rinsing away the debris removed from the filter. In areas where deciduous trees and shrubs are near a pool, the trap must also be frequently emptied, since due to its small size it quickly fills with leaves. By pre-filtering the water with a fine mesh filter, trapping particles as small as 300 microns, before they reach the main pool filter, the main filter can remain in operation for a much longer period of time, clearing the water of even smaller particles. However, fine mesh filters require a large surface area to operate without requiring frequent maintenance due to clogging. Further, since filter/skimmer access portals are preferably small, such that they are inconspicuous and less of a pool-side trip hazard, large-area fine mesh filters cannot be easily fitted or removed through the small access portal.
For these reasons, a filtering apparatus is needed, which provides a more robust skimmer trap or filter and an easily accessible drain line filter adjacent the skimmer, both capable of retaining very small particles. There is also a need for large-sized filters which require only minimal space for access and removal on a pool patio. There is also a need for a filter apparatus incorporating a fill water inlet and an overflow line into the apparatus, and which is also adaptable for incorporating ozone or other purification systems into the skimmer and drain lines. Finally, there is a need for a modular filter apparatus allowing a skimmer pre-filter to be installed by itself, or with a drain line pre-filter as desired.